import java.util.Scanner;
public class test {
    public static void main(String[] args) {

        double sum = 0;
        int flag = 1;
        for (
                int i = 1;
                i <= 100; i++) {
            sum = sum + 1.0 / i * flag;
            flag = -flag;
        }
        System.out.println(sum);
    }
}